The methods and devices for determining quantity and size of the particles and small bodies are now well known, and it is also well known that powerful light or laser and optical system or mirror can be, and have been, heretofore used to achieve particle size and particle quantity measurements. Such devices are well known and described in the articles: R. G. Knollenberg, B. Schuster--"Detection and Sizing of Small Particles in Open Cavity Gas Laser," Applied Optics, Vo.11, No.7, November 1972, pp.1515-1520; R. G. Knollenberg--"An Active Scattering Aerosol Spectrometer," Atmospheric Technology, No.2. June 1973, pp.80-81; Schehl, Ergun, Headrick--"Size Spectrometry of Aerosols Using Light Scattering from the Cavity of a Gas Laser," Review of Scientific Instruments, Vol. 44, No. 9, September 1973; R. G. Knollenberg--"Active Scattering Aerosol Spectrometry," National Bureau of Standards Special Publication, No.412, October 1974, pp.57-64; R. G. Knollenberg, R. E. Luehr--"Open Cavity Laser Active Scattering Particle Spectrometry from 0.05 to 5.0 Microns," Fine Particles, Aerosol Generation Measurement, Sampling and Analysis, Academic Press, May 1975, pp.669-696; R. G. Knollenberg--"Three New Instruments for Cloud Physics Measurements: The 2-D Spectrometer, the Forward Scattering Spectrometer Probe, and the Active Scattering Aerosol Spectrometer", American Meteorological Society, International Conference on Cloud Physics, July 1976, pp. 554-561; R. G. Knollenberg--"The Use of Low Power Laser in Particle Size Spectrometry", Proceeding of the Society of Photo-Optical Instrumentation Engineers, Practical Applications of Low Power Lasers, Vo.92, August 1976, pp.137-152; Elterman--"Brewster Angle Light Trap," Applied Optics, Vol. 16, No. 9, September 1977; Marple--"The Aerodynamics Size Calibration of Optical Particle Counters by Inertial Impactors," Aerosol Measurement 1979; Diehl, Smith, Sydor--"Analysis by Suspended Solids by Single-Particle Scattering," Applied Optics, Vol. 18, No. 10, May 1979; K. Suda--Review of Scientific Instruments, Vol. 51, No. 8, August 1980, pp.1049-1058; R. G. Knollenberg--"The Measurement of Particle Sizes Below 0.1 Micrometers", Journal of Environment Science, January-February, 1985, pp. 64-67; Peters--"20 Good Reasons to Use In Situ Particle Monitors", Semiconductor International, Nov. 1992, pp.52-57 and Busselman et al.--"In Situ Particle Monitoring in a Single Wafer Poly Silicon and Silicon Nitride Etch System", IEEE/SEMI Int'l Semiconductor Manufacturing Science Symposium, 1993, pp.20-26.
The reference in these articles is made to the devices and methods of particle measurement utilizing an open cavity laser. These methods and devices use imaging systems, which are based on lens use, the same as it mentioned, for example, in U.S. Pat. No. 4,140,395, U.S. Pat. No. 4,798,465 and in U.S. Pat. No. 5,495,105 of the prior art.
The other devices mentioned in prior art (for example, U.S. Pat. No. 4,606,636) use a non-divergent quadric reflector. Such devices use a paraboloidal sphere as mirror.
Yet in other prior art (for example, such as U.S. Pat. No. 4,189,236, U.S. Pat. No. 4,523,841, U.S. Pat. No. 5,467,189 and U.S. Pat. No. 5,515,164) we can find the devices (sensors) with ellipsoidal mirrors instead of the lens systems or non-divergent quadric mirrors.
All these devices, mentioned in the prior art above, use light scattering focalizing methods. Such methods are based on the collection of the scattered light. A light scattering occurs at the first focal point (focus) by particles in the laser beam. Considering stochastic dispersion of the scattered light, the devices, mentioned in the above prior art, use mirrors or optics. This is necessary for scattered light collecting and focalizing at the second focal point (focus), where a light detector is placed and intended for scattered light detection.
Another known method uses direct detection, as it mentioned in U.S. Pat. No.5,085,500. By this method, the scattered light in such devices is detected by the light detectors directly with no scattered light collection.
As shown on FIG. 1, related to the use of the optics, regarding the U.S. Pat. No. 4,140,395, No. 4,798,465, and No. 5,495,105, the scattered light 6 is collected by the optical system 10, which is presented by the lenses.
On FIG. 2 is presented the device, using non-divergent quadric mirror, (U.S. Pat. No. 4,606,636). From FIG. 2 we see that the collection of the scattered light is provided by non-divergent quadric mirror 18.
The counting and measuring devices (sensors), mentioned in the U.S. Pat. No. 4,189,236, No. 4,523,841, No. 5,467,189, and No. 5,471,299, using an ellipsoidal mirrors 17, are presented on simplified FIG. 3.
On FIG. 4 is presented the particle sensor by U.S. Pat. No. 5,515,164, also using the ellipsoidal mirror for the scattered light collection. This sensor uses specially increased cross-section outlet area of the particle flow.
On FIG. 5 is shown a simplified drawing of the device, using the direct detection method.
It is understood, that the methods and devices, mentioned of the prior art of the above, require the use of the scattered light collection means and systems (FIGS. 1-4) or very large spatial surface of the light detector or sufficient quantity of the light detectors (FIG. 5). Such methods and/or devices need to include expensive means and systems. Also, the mentioned above methods and devices have a common deficiency, which is characterized by non-consideration of all scattered light plurality (for example, a scattered light 23 on FIGS. 1-5) and non-precise focalizing of the particle flow (for example, a scattered light 7 on FIGS. 1-5).
It is known, that integrated circuits (chips) and semiconductors have been produced in "clean rooms". The air in such "clean rooms" should be very well cleaned. The continuing tendencies of improvement in circuit integration and degree of microminiaturization require corresponding improvements of the environment in "clean rooms" and efficiency of the measuring devices. And now, as known from prior art, the sensitivity of the counting and measuring devices should be at least as small as 0.1 .mu.m (Micron). Some known devices (for example, by U.S. Pat. No. 5,731,875) use a plurality of light emitting lasers intended for the power decreasing, that provides the elimination of the laser heat-sink, but, it requires to use a plurality of fiber optic stands and the optical element(s) for the focusing of a plurality of light beams.
Thus, the unfocused and/or unconsidered (undetected) scattered light in the mentioned above devices of a prior art creates light background (light noises) inside such devices, creating thereby incorrectness of the resulting information about the measured environment. Additionally, such light noises limit the sensitivity of such devices.
Also the devices, based on scattered light collection and some other detection methods (for example, by light splitting), use a different variations of the analog comparison method for the particle counting and measuring. Such methods can be illustrated, for example, by U.S. Pat. No. 4,798,465, wherein is shown the particle size detection device, using one of the particle measuring comparison method variation. The signals from detectors via the amplifiers follow to the comparators, which are connected to the reference voltage means. The amplified detected signal is compared with the predetermined reference voltage for the particle size qualifying.
Such analog methods cannot provide a sufficiently high sensitivity related to the increasing environmental requirements, because of the non-precise analog method of comparison.